A couple of years ago Popular Mechanics fielded a question from a reader in their auto mechanic column. The gist of the letter was that Ford installed a constant voltage sending unit in late model Rangers (and probably other vehicles) so that once any oil pressure was sensed on engine start the gauge read a normal center-of-dial reading. You can see this on start up if you watch how the gauge works. The needle will jump the moment the engine fires to this "normal" position. A true oil pressure gauge would increase its pressure at something other than an instantaneous rate. The editors went on to say that a variable resistance sending unit would probably make the gauge act like we expect it to.
I'm new to the forum. Has anyone heard of this and confirmed it? Has anyone researched and found a sending unit that will make the gauge act like it should?
You are exactly right, the oil pressure gauge on Rangers (and
ther Fords) is an idiot light! The oil pressure sending unit is a
"normally open" switch, that closes with about 7PSI of oil
pressure. When the "switch" closes, the current through the
oil pressure gauge is set by a 20 ohm resistor, mounted on the
back of the instrument panel. This current makes the gauge read
at "half scale", and will not show changes in oil pressure.
You can change the sending unit to an "analog" type of sending
unit, and "short" the 20 ohm resistor, to convert it to a real oil
pressure gauge. I will say, that when I converted my 1999 3.0L
FFV, I DID NOT have the 20 ohm resistor in the back on my
instrument panel, so just ended up changing the sending unit..
This is a very good question...and one that I am looking into myself. Bob has offered me advice on this issue too, and I am getting ready to attempt to fix it using his method. He told me a sending unit from a late 80s model Ranger will work if you change the connector on it. I hope it works!
WHY did Ford even bother with a "dummy" gage? They should either use true pressure gages like GM, or not use one at all like Toyota. Shame on you Ford!
If anyone else has any info. on what model years units will work, please post here. If the '90 model 4.0 sending unit would be "analog", I think that would be an easier swap.
What year of Rangers' are we talking about here? I'm curious to know if mine is a 'dummy' guage or not... '92 4.0L 4x4. I do a lot of highway driving (truck is used for work) and would like to make sure I'm getting a real indication of oil pressure.
From what I have read, all Ford trucks 1986 and newer probably have "dummy" oil pressure gages that jump to a default center-of-dial position when the engine is started, rather than actually measuring fluctuations in pressure.
The only way to fix it is to install an analog "variable resistance" oil pressure sending unit. Problem is, I don't know which model years were equipped with these, and I don't know if they would be a direct swap or not.
What year Ranger (early 80's,...??????) has the sending unit to convert the oil pressure gauge? I have an 01 model with a 3.0 engine. I would like to convert also.
What year Ranger (early 80's,...??????) has the sending unit to convert the oil pressure gauge? I have an 01 model with a 3.0 engine. I would like to convert also.
JEY, if you read through this recent thread from the Oil Forum you'll find the answer to your question
i have a 1991 4.0 auto, my oil pressure gauge works as it should, doesn't stay near the center.
I notice i don't carry anywhere near the center of the guage for pressure but maybe its not working right )
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03 Black SXT
Chill factory stage 2 turbo-275hp, nuff said
2001 Ranger XLT 2wd 2.3 5 speed
Stock, and staying that way
1991 Ford Ranger 4.0 Short Bed 4" lift 235-75s-sold!
Originally posted by 1991rangerford i have a 1991 4.0 auto, my oil pressure gauge works as it should, doesn't stay near the center.
I notice i don't carry anywhere near the center of the guage for pressure but maybe its not working right )
If it is working as a gauge, you will see fluctuations in the needle.
When cold, it will read higher, but when hot, and idling, it should
read lower......If the needle stays in the same place, then you
have an "idiot light" type of gauge....
Hello all, new member here. On the oil pressure gauge thing, I turned mine on my 93 Explorer into a normal gauge. Here's how it worked on my Explorer. Pressure switch turns on if pressure is above 5 lbs I think. This would make the gauge go full deflection, high. They wired in a resistor before it gets to the gauge and that's what brings the needle down to around half and it stays there. I installed a 0-80psi sending unit , removed the resistor from the back of the gauge and ran a jumper wire across it. And now have a working gauge. I just bought a 1995 Ranger, and am assuming it will be the same way, I will tear into it and probably do the same thing to it.
CJ
Thanks for the good replies. I looked for my sending unit where Rogue Performance said it was, behind the right cylinder head and I couldn't find it. At Rogue's website there is a good photo showing the sending unti from behind the engine with the transmission removed. Do you have to remove the tranny to see it? I've change them before and this one looks what I remember, but I can't seem to find mine? Do I just need better glasses?
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